It is known that during the storage and/or transportation of perishable produce its preservation can be enhanced by controlling the atmosphere surrounding the produce. For example, it has been found that an atmosphere in which nitrogen predominates is particularly useful for controlling the preservation of perishable products. Furthermore, in addition to controlling the amount of oxygen present in the atmosphere there has also been found a need to control the amount of other substances which may be present, for example, carbon dioxide and ethylene which might be formed by the produce whilst contained within the container.
In our co-pending European Patent Application No. 91306504.1 (Publication No. 0 467 668 A1) there is described a system for controlling the atmosphere of a container for use in the storage and/or transportation of perishable goods. The system includes adsorption means in the form of a plurality of pairs of beds, each pair of beds being designed preferentially to adsorb from the atmosphere one or more of water vapor, ethylene, carbon dioxide, and nitrogen. Some of the beds are designed to work on a temperature swing adsorption cycle and at least one bed is designed to operate on a pressure swing adsorption/desorption cycle.
Although the system described in our co-pending application achieves all of the requirements in terms of atmosphere control it remains complicated and somewhat bulky and in particular heat is required to assist in the regeneration of the adsorbent beds which are designed to operate on the temperature swing adsorption cycle.
It is an aim of the present invention to provide a simplified system which will achieve the same effect, that is, independent control of the gases likely to be found in the atmosphere of a container for perishable goods.